/**
 * @desc 在树形数据中查询指定节点数据，并返回当前节点
 * @param obj TREE_DATA树形结构 {id: '',children: []}
 * @param id  节点ID
 * @returns {{id: * ,children: []} | null}
 */
export const findItem = (id, obj) => {
  if (obj.id === id) {
    return obj
  }
  const { children } = obj
  if (children) {
    for (let i = 0, len = children.length; i < len; i++) {
      const res = findItem(id, children[i])
      if (res) {
        return res
      }
    }
  }
  return null
}


/**
 * @param {Function} func
 * @param {number} wait
 * @param {boolean} immediate
 * @return {*}
 */
export function debounce(func, wait, immediate) {
  let timeout, args, context, timestamp, result

  const later = function() {
    // 据上一次触发时间间隔
    const last = +new Date() - timestamp

    // 上次被包装函数被调用时间间隔 last 小于设定时间间隔 wait
    if (last < wait && last > 0) {
      timeout = setTimeout(later, wait - last)
    } else {
      timeout = null
      // 如果设定为immediate===true，因为开始边界已经调用过了此处无需调用
      if (!immediate) {
        result = func.apply(context, args)
        if (!timeout) context = args = null
      }
    }
  }

  return function(...args) {
    context = this
    timestamp = +new Date()
    const callNow = immediate && !timeout
    // 如果延时不存在，重新设定延时
    if (!timeout) timeout = setTimeout(later, wait)
    if (callNow) {
      result = func.apply(context, args)
      context = args = null
    }

    return result
  }
}


// 生成UUID
export function createdUUID() {
  function s4() {
    return Math.floor((1 + Math.random()) * 0x10000).toString(16).substring(1);
  }
  return s4() + s4() + s4() + s4() + s4() + s4() + s4() + s4();
}


export function paging(tableData, page) {
  if (tableData.length === 0) {
    return []
  }
  const { currentPage, pageSize } = page;
  const endLength = currentPage * pageSize;
  const startLength = currentPage * pageSize - pageSize;
  return tableData.slice(startLength, endLength)
}
